Electric-arc lamp for search-lights, projectors, and the like.



H. BECK.

ELECTRIC ARC LAMP FOR SEARCH LIGHTS, PROJECTORS, AND THE LIKE.

APPLIQATION FILED NOV.22, 1913.

1,086,31 1 Patented Feb. 3, 1914.

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Fig. 3.

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Wilneaaea I I lnvegur".

HEINRICH BECK, OF MEININ'GEN, GERMANY.

ELECTRIC-ARC LAMP FOB SEARCH-LIGHTS, PROJECTORS, AND THE LIKE.

Specification of Letters Iatent.

Patented Feb. 3, 1914..

Application filed November 22, 1913. Serial no. 802,489.

To all whom, it may concern:

Be it known that I, HEINRICH Back, a subject of the German Emperor, and residing at Meiningen, Germany, have invented certain new and useful Improvements in Electric-Arc Lamps for Search-Lights, Pro jectors, and the like, of which the following isa specification.

My invention relates to an improvement on the methods of working electric arc lamps and of arranging the electrodes for search lights, projectors, and the like, as disclosed in my United States Patent No. 1,029,787.

I have, by the aid of further experiments, found that proper working conditions for are lamps when the electrodes are charged with a high current density may be provided by other means than subjecting the electrodes to the action of an indifferent gas or vapor surrounding the burning end of the positive carbon .while the lamp is.in use. For this it is necessary that means be employed which will deflect. the arc flame proceeding from the negative electrode from the crater-of the positive electrode, and that the current shall emerge essentially at the front end of the positive electrode.

In the accompanying drawing: Figure 1 shows two arclamp electrodes, in the condition of burning which it is the object of my invention to avoid. Fig. 2' shows the electrodes in the condition of burning which is to be obtained through my invention. Fig. 3 is an arrangement of the electrodes by means of which the desired burning condition of the electrodes may be obtained. Figs. 4 and 5 illustrate further arrangements of the electrodes for carrying out the present method.

I have observed that in the burning condition of the electrodes, which it is the object of my invention to avoid, and which is illustrated in Fig. 1, the flame f proceeding from the negative electrode 6, which generally does not contain any light emitting admixtures of metal, metal salts or car-bids, and is thus a so-called pure carbon, envelops the positive electrode a, which contaius such admixtures and this is a flame arc carbon, to a considerable part of its length. The current then not only emerges from the face end'c of the ositive electrode a, but also along the shell d of the electrode. The consequence is that the crater of the positive electrode a is not hollowed out at the face of the end 0,- as I have describedv it with the use of a jet of indifferent gas or vapor enveloping the burning end of the carbon in my U. S. Patent No. 1,029,787,

but the end of the positive carbon a reing to my hereinafter described method, but

without the aid of a jet of indifferent gas enveloping the positive carbon, the current emerges essentially at the face of the end 0 of the positive electrode a. Thecrater of the positive electrode a thereby ishollowed out as indicated in the drawing, to a great depth, and a high intensity is obtained. The flame f proceeding from the negative carbon 7) is then deflected, as shown in Fig. 2, and

the, potential rises from 40 to 43 volts as before to to volts. I have further observed that when using a high current against the middle of the crater of the positive electrode, the positive flame is not permanently able to deflect the negative flame.

Then the burning condition shown in Fig.

1 will appear, in which only a small intensity of light is obtained from the ositive crater, the same remaining practica ly flat. The tongue f of the flame f is, in the position of the electrodes shown in Fig. 1, directed against the center of the face end of the positive electrode a, the point of the core, however, stopping a little short'of the positive electrode.

To avoid the unfavorable condition shown in Fig. 1, in particular the unfavorable flat crater in the positive electrode, and to obtain the favorable condition and a deep hollowing of the positive crater, as shown in Fig. 2, the conditions are so arranged that the tongue f of the negative flame can strike the positive crater in its upper part only, since the electrodes are arranged horizontally and the upward draft of air turns the negative flame upward so that the flame proceeding from the positive carbon can dellect the negative flame, entirely away from the positive crater. Moreover, to obtain the effect shown in Fig. 2, the electrodes may be either exactly coaxial .as shown in Fig. 2, or the axis of the negative carbon may be a little above the axis of the positive carbon, as shown in Fig. 3. The tips of the electrodes may, also, be atan angle to each other as shown in Fig. 4. A further method of obtaining the favorable burning condition shown in Fig. 2, consists in the production of a very high vapor pressure at the positive electrode. When the vapor pressure is sufficiently high, it will likewise produce a deflection of the negative flame from the center of the crater. For producing the necessary high vapor pressure, an unusually high current density is used in the positive electrode. For instance, the diameter of a I is for this purpose made extremely small as say 20 mm., and this carbon is required. to carry 120 amperes or more. These positive carbons Wlll always be such as contaln llght emitting admixtures in the form of metal or metal salts, carbids, or the like, which are well known in the art. The negative carbon, on the other hand, is generally pure carbon. At so high' a current density for producing a very high vapor pressure, the combustion of the positive electrodes is very .rapid. The combustion may for instance,

amount to 400mm. in an hour, so that the quantity of electrode substance evaporated within a time unit is very considerable. It will be understood, however that I do not de sire to limit myself to the particular method of increasing the vapor pressure just mentioned, since other methods Wlll suggest themselves.immediately to those accustomed to making and using the so-called flame .arc carbons. Still another method of defleeting or deviating the tip of the negative crater of the positive electrode by means of v a fine jet of an indifferent gas issuing from a nozzle h under a suitable pressure. This finer-jet of gas need'not, however, envelop the burning end of the positive carbon.

Other known methods of deflecting an arc may of course be substituted for the mechanical blast without departing from the spirit of my invention.

The previously described means for obtaining a deep hollowing of the positive carbon crater may be employed either singly or any number of them at the same time, also without departing from the spirit of my invention;

Having thus described my what I claim is 1. The method of operating arc lamps which consists in employing a high current density which produces a tongue in the negative .flame and deflecting said tongue from the center of the positive electrode.

2. The method of operating arc lamps invention,

which consists in employing a high current HEINRICH BECK.

\Vitnesses v S. HINZE, FR. MI'JLLER. 

